The present invention relates to electronic circuits, and more particularly to electronic circuits for providing a reset signal to another electronic circuit.
Most programmed or programmable type logic circuits must be set in a zero state or reset state when powered on to assure that their constitutive elements do not present undetermined logic states. The power on reset (POR) circuits provided for this deliver a reset signal when the supply voltage rises and reaches a first switching threshold V1, and release the reset signal when the voltage reaches a second switching threshold V2. According to the chosen convention, the active value of the reset signal may be 1 or 0. The release of the reset signal corresponds to its setting to 0 in the first case and to its setting to 1 in the second case.
Electronic circuits may implement a reset signal with a positive polarity or a negative polarity. Existing reset signal generators lack the ability to detect whether the circuit to which the reset signal is directed requires a negative polarity active reset signal or a positive polarity active reset signal. As a result, both positive polarity and negative polarity reset signal generators must exist in the marketplace. Use of the wrong signal generator is a design flaw that requires redesign.
Therefore, there is a need in the art for a circuit that detects the required polarity of a circuit""s reset signal and provides a reset signal of the appropriate polarity.
In one aspect, a reset driver circuit for generating an input reset signal for a second circuit is provided. The reset driver circuit comprises means for generating a first signal indicative of a required characteristic of an input reset signal for a second circuit; means for comparing the first signal and a second signal indicative of a characteristic of a first input reset signal; and means for generating a second input reset signal that includes the required characteristic of an input reset signal for a second circuit.
In another aspect, a method of generating an input reset signal is provided. The method comprises generating a first signal indicative of a required characteristic of an input reset signal for a second circuit; comparing the first signal and a signal indicative of a characteristic of a first reset signal; and generating a second reset signal that includes the required characteristic of an input reset signal for a second circuit.
In another aspect, a reset driver circuit for generating an input reset signal for a second circuit is provided. The reset driver circuit comprises a flip-flop having an input connected to the reset input of a second circuit; a first comparator including a first input connected to a first output of the flip-flop and a second input that receives an external reset signal; a second comparator including a first input connected to a second output of the flip-flop and a second input that receives an external reset signal; a first switch connected to the output of the first comparator for selectively connecting the reset input of the second circuit to a first voltage; and a second switch connected to the output of the second comparator for selectively connecting the reset input of the second circuit to a second voltage.
In yet another aspect, a reset driver circuit for generating an input reset signal for a second circuit is provided. The reset driver circuit comprises a first flip-flop having a first input for receiving a reset input signal, and generating a first signal indicative of a characteristic of the reset input signal; a second flip-flop having an input connected to a reset input pin of a second circuit and generating second and third outputs indicative of a characteristic of the reset input pin; a digital logic circuit for comparing the first output with at least one of the second output and the third output; a first switch connected to the output of the digital logic circuit for selectively connecting the reset input of the second circuit to a first voltage; and a second switch connected to the output of the digital logic circuit for selectively connecting the reset input of the second circuit to a second voltage.